Objective: Assess the relative effects of a variety of illicit and licit drugs on risk for adverse birth outcomes.
Methods: We used data from two large prospective investigations, and a novel analytic method, recursive partitioning class analysis to identify risk factors associated with preterm birth and delivering a small for gestational age infant.
Results: Compared to cocaine and opiate non-users, cocaine users were 3.53 times as likely (95% CI: 1.65-7.56; p = 0.001) and opiate users 2.86 times as likely (95% CI: 1.11-7.36; p = 0.03) to deliver preterm. The odds of delivering a small for gestational age infant for women who smoked more than two cigarettes daily was 3.74, (95% CI: 2.47-5.65; p<0.0001) compared to women who smoked two or less cigarettes daily and had one previous child. Similarly, less educated, nulliparous women who smoked two or fewer cigarettes daily were 4.12 times as likely (95% CI: 2.04-8.34; p < 0.0001) to have a small for gestational age infant.
Conclusions: Among our covariates, prenatal cocaine and opiate use are the predominant risk factors for preterm birth; while tobacco use was the primary risk factor predicting small for gestational age at delivery. Multi-substance use did not substantially increase risk of adverse birth outcomes over these risk factors.